Reference is made to co-pending U.S. application Ser. No. 07/778,402, filed Oct. 17, 1991, to Philip J. Mott, entitled "Single Pin Rocker Joint Bushing Chain," which is related to the subject matter of the present application and is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to power transmission chains and particularly to an improved rocker joint for such chains. The rocker joint is formed from a single pin and an associated link aperture. The invention has application to power transmission chains of the silent chain variety, as well as power transmission chains for use with variable pulley transmissions (continuously variable transmissions).
2. Description of the Prior Art
Power transmission chains are widely used in the automotive industry. Such chains are used for engine timing drives as well as for the transfer of power from the engine to the transmission or for the transfer of power in a transfer case. Power transmission chains are also widely used in industrial applications.
One type of power transmission chain is referred to as "silent chain". Such chain is formed of interleaved sets of inverted tooth links. A set or rank of links is assembled from several links positioned alongside of or laterally adjacent to each other. Each link has a body with a pair of spaced apertures and the apertures of one set of links are arranged and aligned with the apertures of the next adjacent set of interleaved links. The links have a pair of depending toes separated by a crotch.
The links are connected by pivot means, which are typically round pins received in the link apertures. The pivot means can also comprise a rocker joint, which may include a pin and a rocker. Each pin and rocker has a front face which contact and rock on each other. An example of silent chain is found in U.S. Pat. No. 4,342,560, which is incorporated herein by reference. An example of silent chain which can be used in engine timing applications is found in U.S. Pat. No. 4,759,740, which is also incorporated herein by reference.
A second type of power transmission chain is used to transfer power between a pair of variable pulleys in a continuously variable transmission. The chain links are provided in sets that are interleaved together. The links have aligned apertures for receiving pivot means. The pivot means can provide the means for the transfer of power between the chain and the sheaves of the pulley by allowing the sheaves to directly contact the ends of the pivot means in a driving engagement.
Load blocks or load carrying means that are positioned on the chain between the spaced pivot members can also provide the means for transfer of power between the pulleys. The load blocks can be in the form of struts that are carried in a passageway below the links. Alternatively, the load blocks can extend around the links of the chain and have one or more windows for receiving the chain links therein. The load blocks have tapered outer or end surfaces which engage the sheave faces of the pulleys to provide the driving engagement between the pulleys and the chain. Examples of power transmission chains suitable for use in a continuously variable transmission are shown in U.S. Pat. No. 4,911,682, U.S. Pat. No. 4,507,106, and U.S. Pat. No. 5,007,883, which are incorporated herein by reference.
The present invention relates to an improved rocker joint for power transmission chain. Rocker joints for chains are known in the art. Rocker joints are utilized in an attempt to attain higher efficiencies and less wear than comparable round pin joints. Round pin joints typically produce higher wear as a result of the sliding action between the round pin and the inside of the circular link aperture, as the chain articulates. In contrast, rocker joints provide a lower wear joint on account of the rocking action between the pin and the rocker portion, as the chain articulates.
U.S. Pat. No. 4,507,106 discloses a rocker joint in which, in the preferred embodiment, each pin or rocker has the identical cross-section. Each pin has a front surface which rocks on the front surface of the adjacent pin. In the preferred embodiment, the pins have a front surface defined by a first radius, and a back surface defined by a second and a third radius, both progressively smaller than the first radius. The rocker joint comprises a pair of pins fitted into each group of aligned apertures in the interleaved sets of links to join the links and permit articulation.
U.S. Pat. No. 4,911,682 discloses a rocker joint that includes a pair of pins. The rocker joint has apertures that are a generally hour-glass shape with the enlarged ends receiving the pins. The front surfaces of the pins rock against one another, while the back surfaces of the pins are prevented from substantial rotation by the curvature of the apertures.
These prior art patents represent examples of rocker joints utilizing two pivot members or pins, or a pin and a rocker. The present invention relates to single pin rocker joints in which a single pin rocks against the link aperture. U.S. Pat. No. 2,667,791 discloses a silent chain with a single pin rocker joint. The chain has a single pin with an arcuate periphery, defined by a single radius, and a relatively flat bearing surface. The link has a generally semi-circular aperture with an arcuate bearing surface. The flat surface of the pin rocks against the arcuate surface of the link aperture.
Another type of single pin rocker joint is shown in U.S. Pat. No. 4,337,057. The patent discloses a double unrolling hinge for a chain-belt for a variable pulley transmission. Both sides of the hinge pin contact the insides of the link apertures.
U.S. Pat. No. 1,564,798 also discloses a single pin, double-edged rocking joint. The pin is thicker in the center section than at the top and bottom. The formation of the link aperture allows the sides of the pin to roll against the aperture sides of adjacent, interleaved links.
The present invention provides an improved single pin rocker joint for a power transmission chain. The construction of the pin includes a substantially flat rocking surface and an arcuate surface formed of a plurality of radii. A clearance between the back surface of the pin and the associated aperture permits movement of the pin with respect to the aperture. The chain includes inside links and guide links and has application in timing drives as well as drives for continuously variable transmissions.